This invention relates to cadmium selenide photoconductive devices and more particularly to photoconductive devices employing cadmium selenide bodies which include a blocking contact, or heterojunction, similar in electrical characteristics to a p-n junction.
Cadmium selenide bodies are known which display high photosensitivities when employed in photoconductive light sensitive devices. This and other advantages makes such cadmium selenide bodies particulary desirable for use in photoconductive imaging devices such as camera tubes, or as coatings for electrophotographic plates. Unfortunately, unstable and/or high dark currents normally associated with such prior art photoconductive bodies, have precluded their general commercialization in light sensitive devices.
Recently, researchers in the field of cadmium selenide photoconductors have sought to improve the dark current characteristics associated with cadmium selenide bodies by incorporating an overlayer of cadmium salt of oxy-acid on a base layer of cadmium selenide by somewhat complicated processing methods. The purpose of this overlayer is to stablilize and reduce the dark current by forming a blocking contact to electrons within the body whereby the body may be depleted in a manner analogous to a p-n junction. Such a photoconductor body is, for example, described in U.S. Pat. No. 3,816,787, issued to K. Shimizu et al. on June 11, 1974. Alternative cadmium selenide bodies having low and stable dark current characteristics are, however, desired wherein less complicated methods may be employed for their manufacture.